Re: Measuring high impedance filters

Rod Wall
 

This may help,
 
Read the section on “Complex conjugate matching” at:
 
A Calculator:
You will need to 1st measure the centre frequency complex impedance for the ports for the filters. Might be easier to 1st search for the manufacturer's specifications. 
 
Regards,
 
Roderick Wall.
 
From: n5ib@...
Sent: ‎Sunday‎, ‎October‎ ‎6‎, ‎2013 ‎7‎:‎34‎ ‎AM
To: PHSNA@...
 
 



Hi Nick,
 
I'd think you could use a broadband transformer. It ought to do OK over the fairly limited bandwidth of the filters.
For 50:2000 you'd need about a 1:6 turns ratio. And the reactance of the high-turns winding ought to be around 2000 ohms or better. That's around 70 uH at 5 MHz.
Ferrite cores should serve.
 
Or maybe a combination of techniques... 4:1 quadrafilar transformer to give 50:800 then attenuator pad to handle the remaining transformation. Wouldn't have to introduce so much loss, so maybe the level would be high enough for decent dynamic reange.
 
Jim, N5IB
 

 

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